The proposed research covers four areas. The first area is the development of a specific, sensitive assay for UDPGlcNAc 2-epimerase. The assay will employ UDP(2-H3)-GlcNAc as substrate, and measure the rate of H3 released to the medium. Using the new assay Morris and Novikoff hepatomas will be examined for UDPGlcNAc 2-epimerase activity. The effect of insulin on the expression of 2-epimerase in these hepatoma lines will also be investigated. The second area of study will be analysis of Morris and Novikoff hepatomas for free and bound sialic acids. The third area will be a study of the mechanism of action of UDPGlcNAc 2-epimerase particularily in attempting to distinguish between two proposed mechanisms; one involving a glycal intermediate and the other involving a glycosyl enzyme intermediate. The fourth area will be a study of the pathway for the biosynthesis of UDPManNAc-UA, and isolation of the enzymes unique to this pathway.